1. Active and Passive Transport

2. Vocab: Hypertonic: More solutes than the other solution
Hypotonic: Less solutes than the other solution
Isotonic: Equal solutes as another solution

3. Describing a solution
Hypotonic: when a solution is less concentrated than another solution
Example: if around a cell is hypotonic, then water will move into the cell.
Can cause a cell to get so large it may burst (cytolysis)

4. Hypertonic: When a solution is more concentrated than another solution
If around a cell is hypertonic, water will move out of the cell
Can cause the cell to get very small (in plants will see plasmolysis: wilting)

5. Isotonic: when two solutions have the same concentration (are at equilibrium)
Causes water to move in and out equally
The cell maintains its shape

6. Hypotonic solution
Isotonic solution
Hypertonic solution
(a)
(b)
H2O
Lysed
Normal
Shriveled
Turgid (normal)
Flaccid
Plasmolyzed

7. Passive Transport

8. S-B-7-3_Passive Transport PPT
Process that moves materials across the plasma membrane
Does not require energy from the cell
Materials move with the concentration gradient:
high concentration low concentration
3 Kinds:
Diffusion, Osmosis, and Facilitated Diffusion
S-B-7-3_Passive Transport PPT

9. S-B-7-3_Passive Transport PPT
Diffusion
The movement of molecules across a membrane, with a net movement from high to low concentration
Molecules tend to “spread out” to reach equilibrium.
Source:
S-B-7-3_Passive Transport PPT

10. S-B-7-3_Passive Transport PPT
Osmosis
Diffusion of water across a selectively permeable membrane.
Does not require energy from the cell.
S-B-7-3_Passive Transport PPT

11. S-B-7-3_Passive Transport PPT
The rule for osmosis: If the area outside the cell has more salt, then water will be sucked out of the cell.
S-B-7-3_Passive Transport PPT

12. Facilitated Diffusion
Carrier proteins help small molecules move across the plasma membrane.
Does not require energy from the cell.
Source:
S-B-7-3_Passive Transport PPT

13. Passive Transport: Review
Diffusion, Osmosis, Facilitated Diffusion
Molecules move with the concentration gradient
Does not require energy from the cell
S-B-7-3_Passive Transport PPT

14. What if…..
Environment around a cell is hypotonic. What direction will the water move?
Salt?

15. What if….. The environment around a cell is hypertonic.
What direction will the water move?
Salt?

16. 2. Active Transport Requires energy
Goes against the concentration gradient (from lower concentration to higher concentration)

17. Active Transport:
Molecules move across the cell membrane from ____low________ to ___high______ concentration. It uses __energy_______ or ATP.
Carbon Dioxide molecules

19. __Molecular ____ ___transport____ (pumps)- proteins use ATP to _transport_____ molecules across the cell membrane from __low____ to _high____ concentration.
This allows _small___ _molecules_ and _ions__ (such as K+_, __Ca__, _Na___) to be transported across the membrane.

20. _Endocytosis__ - the _cell___ _membrane_ surrounds substances and moves them _INTO_ the cell.

21. Ex: White Blood Cells, which are part of the immune system, surround and engulf bacteria by endocytosis.

22. __Phagocytosis__- surrounds a _food__ _molecule_. Cell “__eating___”
_Pinocytosis__ - surrounds __liquid_.
Cell “__drinking___”

23. _Exocytosis__ - a _vacuole__ joins with the cell membrane and _releases_ its contents.

25. What leaves through exocytosis?
Cell products: _lipids_ and _proteins__
Cell _wastes__
Excess _water_: through _contractile__ _vacuole_

26. Figure 7.16 The sodium-potassium pump: a specific case of active transport
Cytoplasmic Na+ binds to
the sodium-potassium pump. 1
Na+ binding stimulates phosphorylation by ATP. 2
K+ is released and Na+
sites are receptive again;
The cycle repeats. 3
Phosphorylation causes the
protein to change its conformation, expelling Na+ to the outside. 4
Extracellular K+ binds to the
protein, triggering release of the
Phosphate group. 6
Loss of the phosphate
restores the protein’s
original conformation. 5
EXTRACELLULAR
FLUID
[Na+] high
[K+] low
CYTOPLASM
[Na+] low
[K+] high
Na+ P
ATP
ADP
P i K+

27. Sodium Potassium Pump
Cells usually have more sodium ions outside and more potassium ions inside
Pump increases number of ions where concentration is already high

28. When substances are too large to pass through the cell membrane, use endocytosis or exocytosis
Membrane folds around substances and release into cell or out of cell

29. Figure 7.20 Exploring Endocytosis in Animal Cells
EXTRACELLULAR
FLUID
Pseudopodium
CYTOPLASM
“Food” or
other particle
Food
vacuole
1 µm
of amoeba
Bacterium
Food vacuole
An amoeba engulfing a bacterium via
phagocytosis (TEM).
PHAGOCYTOSIS
PINOCYTOSIS
Pinocytosis vesicles
forming (arrows) in
a cell lining a small
blood vessel (TEM).
0.5 µm
Plasma
membrane
Vesicle

30. Endocytosis Material moved into cell Forms vesicle
Pinocytosis: Liquids
Phagocytosis: Solids

31. Exocytosis
Material released to outside of cell